This invention relates to a needle-threading apparatus for a two-needle sewing machine.
Needle-threading is one of the most complicated and labor-intensive operations in sewing. An apparatus as shown in FIG. 6 has previously been proposed for making these operations more convenient and laborsaving.
The needle-threading apparatus shown in FIG. 6 has a frame member F which is mounted on a sewing machine head (not shown). Frame member F is parallel to a needle bar 1, and is vertically and slidably movable.
A loaded tension spring S2 is held in position by fixing its lower end to the frame member F and its upper end to a retainer 5 thereby normally urging frame member F upward. A shaft 2 is rotatably supported on frame member F.
A pin 3 passes through shaft 2 with both ends of the pin extending out on either side of shaft 2. One end of pin 3 is engaged in an oblique slot Fa in frame member F as shown in FIG. 7A.
A coil spring S1 is helically mounted on shaft 2. The upper end of spring S1 presses against frame member F and its lower end presses against pin 3. This pressure on pin 3 urges shaft 2 downward, thereby forcing pin 3 to the lower end position in oblique slot Fa as shown in FIG. 7A.
A stopper 4 is secured to the needle bar 1. When the frame member F is lowered against the bias of spring S2 by pressing on lever L which forms part of frame member F, pin 3 abuts against the top of stopper 4. Further downward movement of frame member F allows pin 3 to slide upward in the oblique slot Fa as shown by the arrow in FIG. 7A, thereby rotating shaft 2.
A thread catcher 6 is provided in the lower portion of shaft 2. Said catcher includes a hook 6a and needle holders 6bon either side of the hook. The thread catcher 6 is adapted for downward movement and rotation with shaft 2. When pin 3 is in the upper end of oblique slot Fa, shaft 2 cannot rotate and thread catcher 6 thereby engages a needle N on needle bar 1, as shown in FIG. 7B.
FIG. 7C is a partial side view, in perspective, showing the manner in which thread catcher 6 engages needle N. When pin 3 is in the upper end of slot Fa, hook 6a on thread catcher 6 passes through needle eye O of needle N and engages thread. The restoring force of spring S2 then releases frame member F from its downward depression to assume its original position, thereby rotating shaft 2 and removing the now threaded hook 6a through needle eye O.
As aforementioned, the needle threading apparatus is capable of readily and quickly threading needle eye O, thereby improving the sewing operation.
Although the needle-threading apparatus described above may be applied to "one-needle sewing machines", this apparatus is essentially unsuitable for "two-needle sewing machines" where there are not only two needles, N1 and N2, but two needle eyes 01 and 02 which are positioned out of alignment with each other, thereby requiring more space than is here ordinarily available.
For this reason, complicated manual operations are required to thread the two needles, thereby decreasing the efficiency of sewing operations.